AFP/Getty ImagesFrench troops and Malian soldiers enter the historic city of Timbuktu on Jan. 28.

The U.S. and France are moving to create an intelligence hub in Niger that could include a base, near Mali’s border, for American drones that could monitor al Qaeda-linked militants in Mali’s vast desert north, U.S. officials said Monday.

The moves show the extent to which the U.S. and France are girding for what could be an open-ended campaign against the militants in North and West Africa.

U.S. and French officials said they see Niger as a logical hub for intelligence-collection operations nearby in Mali, where France has deployed warplanes and ground troops to drive Islamist militants from cities and towns they have held for months. War planners say small air strips in Niger could be used as launching pads for spy missions and strikes.

The signing of the so-called status-of-forces agreement with Niger was a necessary precursor for American military operations there, officials said. U.S. officials said discussions with Niger on a drone base were at an early stage.

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The U.S. and Niger started negotiating the status of forces agreement last year to provide legal protections for American military personnel operating in the country. Talks took on added urgency after France launched its military mission in Mali on Jan. 11 against al Qaeda in the Islamic Maghreb, or AQIM, and affiliated Islamist militants in northern Mali. The agreement is likely to be announced in Niamey, Niger’s capital, on Tuesday, U.S. officials said.

The agreement signed Monday with Niger is meant to expand cooperation “to counter shared threats in the region,” a U.S. defense official said.

U.S. officials said the agreement doesn’t set out the precise number of American military personnel who would be based in Niger, nor does it prescribe what roles they will play. There are now fewer than 50 U.S. military personnel there.

U.S. operations in Niger to aid the French military campaign would represent a significant escalation by the U.S.

U.S. officials said new drone bases are needed near Mali to monitor militant activity because the U.S. doesn’t have any in or near the new war zone.

Western war planners say small landing strips in Niger near the border with Mali are ideally located for missions using drones, manned surveillance aircraft and possibly U.S. special-operations units. That is because the airstrips in Niger are closer to militant havens in northern Mali than airstrips near Mali’s capital, Bamako, in the south of the country.

The Obama administration has been wary of getting pulled into a new conflict in Mali, but hasn’t ruled out the use of armed drones or special-operations units to help target al Qaeda militants—if intelligence agencies conclude that they are plotting attacks against the U.S. homeland, U.S. officials said.

The Wall Street Journal reported this month that the U.S. was ramping up intelligence collection efforts over Mali, and considering deploying unarmed drones and providing targeting information to the French. The New York Times reported on its website on Monday that the U.S. military command for Africa, known as Africom, was making preparations to establish a drone base in Niger or possibly another nearby country.

Africom declined to discuss any plans for deploying drones—which are sometimes called “ISR,” in military parlance—to Niger. “We don’t discuss specific planning efforts, and in particular, we do not discuss specifics related to ISR, and intelligence matters,” said Col. Tom Davis, a spokesman for the command.

American military personnel in Niger would likely provide counterterrorism training to local forces and help the country with border security, in addition to helping gather intelligence on al Qaeda in Mali, officials said.

Other countries in the region are also seen by U.S. officials as possible hosts for drone bases.

U.S. and French officials are concerned about any spillover of the fighting into neighboring countries, including Algeria, which, at the urging of Paris, has moved forces to try to close its long desert border with Mali. French officials said the goal is to prevent fighters from crossing the border to escape advancing French and African forces.

U.S. officials said they want to step up cooperation with the government in Algiers to fight AQIM and associated militant groups, as Algeria is one of the few capable governments in North Africa that fervently oppose Islamist militants. Current and former officials said the Central Intelligence Agency or the U.S. military may be able to reach a deal in which Algeria provides a drone base in exchange for equipment and training.

The Algerians have been fighting Islamist militant groups since the 1990s, when they stepped up their effort to counter extremists with the help of the CIA. The agency forged a good relationship with its counterparts there and Algeria was able to tamp down the threat considerably.

The Pentagon has small numbers of personnel and equipment scattered across Africa. The largest concentration is at Camp Lemonnier, a French-U.S. base in Djibouti, used to launch drone strikes in Yemen. The base is the headquarters for a task force of 2,000 Americans.

In addition to the U.S. personnel now in Niger, about 100 were sent to the region last year to help in the hunt for the Lord’s Resistance Army, a rebel militia in central Africa. Africom is based in Germany, and has personnel on the continent at regional African organizations, such as the African Union.

The agreement with Niger, “would provide a U.S. foothold, a launching pad, in the region to try to stem the threat of Islamic extremism in the region,” said Seth Jones, a former Pentagon adviser and an al Qaeda specialist at the Rand Corp.

He said U.S. officials have a “very serious concern” that even if the French succeed in Mali, the Islamic extremist threat will continue to spread in the region in countries such as Mauritania, Nigeria and Niger.

After a two-week legal and policy review, the White House agreed to provide three air tankers to refuel French warplanes over Mali. The U.S. also is providing cargo planes to transport French troops and equipment.

The U.S. military has forged a relationship with its counterparts in Niger for a decade, dating to the aftermath of the 9/11 attacks, Mr. Jones said.

The Niger military staged a coup in 2010 after then-President Mamadou Tandja attempted to extend his term. The military junta scheduled a presidential election for 2011, returning power to civilian authorities and clearing the way for stepped-up U.S. military support.